Need expert opinion on PS/2 port.

[wwusa83]

Hello everyone,

I recently had a problem with my ps/2 keyboard not working. I read online that it may be the ps/2 port and that a CMOS reset (taking cmos battery out, waiting and putting battery back in) might fix the problem. Sure enough it worked like a champ and I am now typing this message using my ps/2 keyboard.

The problem has been solved, however I don't really know why it happened. For information, the problem first appeared after I switched my mobo to a new case and added a media card reader (via usb mobo header). Is this related? I honestly don't know. It would be great if an expert on how the I/O systems on mobos worked could chime in and give me an explanation. Its really bugging me. Thank you.

 

[hunter315]

Did you try rebooting before removing the CMOS battery?

I have seen many systems with PS/2 keyboards that if you unplug it while the system is on and plug it back in it wont always work, i have also seen others where if its unplugged even for a second after you hit the power button it wont work until you reboot. PS/2 is a lot more finicky than USB is and has more issues with hot plugging.

 

[wwusa83]

Did you try rebooting before removing the CMOS battery?

I have seen many systems with PS/2 keyboards that if you unplug it while the system is on and plug it back in it wont always work, i have also seen others where if its unplugged even for a second after you hit the power button it wont work until you reboot. PS/2 is a lot more finicky than USB is and has more issues with hot plugging.

I did try a a reboot, and I tried shutting down completely, plugging it back in and booting back up. I've also noticed that the media card reader is running much faster now since I cleared the CMOS. Its was very sluggish before. Very confusing.

 

[ko888]

Clearing the CMOS probably forced the system to properly reassign IRQ's and memory mapped IO ranges.

IRQ conflicts usually result in the symptoms you have experienced. The PS/2 keyboard port doesn't like to share an IRQ. USB is designed from the beginning to share an IRQ. If both of these IO ports/hubs were assigned the same IRQ then the PS/2 port just won't respond and the USB port will respond at less than optimal performance.

 

[wwusa83]

Clearing the CMOS probably forced the system to properly reassign IRQ's and memory mapped IO ranges.

IRQ conflicts usually result in the symptoms you have experienced. The PS/2 keyboard port doesn't like to share an IRQ. USB is designed from the beginning to share an IRQ. If both of these IO ports/hubs were assigned the same IRQ then the PS/2 port just won't respond and the USB port will respond at less than optimal performance.

That makes complete sense. Thank you for answering. I thought IRQ conflicts were an old school problem. Any idea why this may have happened? Is it a fluke? Thank you.

 

[wwusa83]

Best answer selected by wwusa83.

 

[ko888]

That makes complete sense. Thank you for answering. I thought IRQ conflicts were an old school problem. Any idea why this may have happened? Is it a fluke? Thank you.

Sometimes the automatic IRQ assignment doesn't work quite right. Sometimes it can be attributed to a deficiency in the BIOS code.